ISOLATION levels

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From: *** (deacdb2_at_hotmail.com)
Date: 06/25/04 

Date: Thu, 24 Jun 2004 20:58:28 -0700

What do you think about these statements?

It seems to me that isolation levels only affect reads (SELECT statements) in the current transaction because isolation levels only affect how S locks are used.

If the transaction contains only INSERT, UPDATE or DELETE, isolation level doesn't matter since they all use X locks.

So in the transaction below, even READ UNCOMMITTED would work the same as SERIALIZEABLE since there are no SELECT statements. I've done quite a bit of testing to try to break it and I can't. What's wrong with my thinking?

BEGIN TRANSACTION
    UPDATE savings SET Balance = Balance - 1000 WHERE SSAN = 555-55-5555;
    UPDATE checking SET Balance = Balance + 1000 WHERE SSAN = 555-55-5555;
COMMIT -- or ROLLBACK

I must confess that when it comes to critical data like money I tend to use SERIALIZEABLE anyway, perhaps to avoid lawsuits. ;-)

thanks,
***

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